Headbox method and means for blending of multiple jets



May 26, 1970 w. B; BOY(C=E ETAL HEADBOX METHOD AND MEANS FOR BLENDING OFMULTIPLE JETS Filed Nov. 29, 1966 2 Sheets-Sheet 1 [NVENTUR5 mum/w 5. 50v65 Jseorv/e pfieez/wsx/ i ATTORNEYS May 26, 1970 w, B BOYCE EI'AL3,514,372

HEADBOX METHOD AND MEANS FOR BLENDING 0F MULTIPLE JETS Filed Nov. 29.1966 2 Sheets-Sheet 2 I N VENTOR5 VV/LL/AM 5. flax c5 Jaea/we P eez/msK/BY M .'\TT()RNEYS United States Patent 3,514,372 HEADBOX METHOD ANDMEANS FOR BLENDIN G 0F MULTIPLE JETS William B. Boyce, Rockton, Ill.,and Jerome P. Brezinski,

Neenah, Wis., assignors to Beloit Corporation, Beloit,

Wis., a corporation of Wisconsin Filed Nov. 29, 1966, Ser. No. 597,738Int. Cl. D21f 1/06 US. Cl. 162-216 8 Claims ABSTRACT OF THE DISCLOSUREMethod of and means for delivering stock to the travelling forming wireof a papermaking machine. The stock is delivered under pressure from adistributor to a chamber having a slice opening to the forming Wire.Inside the chamber the stock is divided into a plurality of separatestreams in expanding diffuser nozzles in which the velocity of the stockis decreased, then the stock is discharged to flow in separate streamsthrough flow passages in a flow element after which the streams aremerged with one another, thereby eliminating eddy currents andcross-currents upstream of the slice.

This invention relates to the handling of fluid slurries, and moreparticularly, to the maintenance of desired fiber dispersions in stockslurries such as papermaking and the like. Specifically, the presentinvention is directed to a method and means for controlling the mixingor blending of multiple jets so that undesirable flow patterns such asvortexes do not develop in the fluid.

Prior attempts to establish uniform distribution of fibers in the stockslurry and to maintain fiber distribution, once established, along thefiow path or stream in the head box in the so-called pre-slice areaprior to disposition of the stock on the forming surface have involvedemployment of complicated auxiliary equipment used to mechanicallyvibrate, shake or stir the stock, all of which actions induce turbulentflow of currents of large amplitude in the stock slurry.

For example, such devices as rectifier and stave rolls, perforatedplates, rod banks, baffles, etc., have been used to control crosscurrents and other undesirable flow patterns which are caused in theslurry passing through the head box. The disadvantages of those deviceswhich align the flow in the machine direction by presenting a resistanceto the flow is that they cause a turbulent wake, since the streams whichthey divide the flow into must coalesce downstream of the device. Theeffect is diminished by having a higher percent open area, as forexample, in a rectifier roll. However, the flow-aligning capacity issomewhat less than desired, and the narrower land area can cause fiberhang-up and lumps. Further, a rectifier roll must rotate to remainclean, making it and its auxiliary equipment expensive.

One such method used to eliminate eddy currents in fiow boxes of highproduction papermaking machines is disclosed in an application Ser. No.459,311, filed May 27, 1965, now Pat. No. 3,400,044, which is assignedto the same assignee.

Therefore, one of the primary objects of the present invention is toprovide means for blending a plurality of stock jets in such a manner soas to substantially eliminate eddy currents or cross currents within theflow box of high production papermaking' machines.

Another important object of the present invention is to provide animproved method and apparatus for effecting the desired distribution offibrous material in a liquid vehicle, such as the fibers in apapermaking stock or slurry, by use of a stock flow controlled methodand means which include at least one sequence or bank or devices whicheffeet a high entrance loss, minimum velocity head gradient or variationin the downstream flow, and a high percentage opening area at the exitside so as to obtain stable flow through the slice.

A feature of the present invention is the use of a flow element which ispositioned downstream of a plurality of stock diffuser nozzles, andwhich flow element provides uniform blending of jet streams when theycoalesce.

Briefly, fibrous material in liquid suspension is delivered to a flowbox or pre-slice chamber, and thereafter through a slice onto a formingwire. A distributor is positioned within the pre-slice chamber todistribute the stock to a plurality of diffuser nozzles or other flowresistance devices. The distributor is so arranged as to providesubstantially the same pressure at the entrance of each diffuser nozzle.The stock is forced through the diifuser nozzles and thereaftersubjected to a flow element, which has a plurality of individualcompartments each positioned in front of a corresponding diffusernozzle. The flow element has a greater cross-sectional open area thanthe open area of the diffuser nozzles. This feature allows the stock todiverge within the passage formed by the side walls of the flow elementthereby expending much of its kinetic energy part of which is convertedinto pressure. As the stock moves through the fiow element the velocitythereof is substantially reduced due to the high percentage open area ofthe flow element. Therefore, as the stock leaves the flow element itwill blend or coalesce uniformly and be substantially free of eddycurrents, as compared to prior art devices which merely reduce theamplitude of such eddy currents.

The stationary fiow element of the present invention has a high openarea of approximately 84%, and as a result there is little turbulentactivity downstream caused by blending of the jets from the individualcompartments of the flow element. The upstream side of the stationaryflow element has an open area of 84% as well, and the thin partitionwalls are kept free from fiber buildup by turbulent activity andback-flow induced by the tube bank diifuser jets. There also exists anextremely turbulent zone between the diifusers and the stationary flowelement which dissipates part of the kinetic energy of the jets.Furthermore, the large amount of solid surface ofifered by thestationary flow element compartments also absorbs kinetic energy of thediffuser jets, and slows the jets down which also aids in the conversionof jet kinetic energy to pressure energy.

Other objects and features and advantages of the present invention willbecome apparent to those skilled in the art from the following detaildescription when taken in conjunction with the accompanying drawingswherein like reference numerals throughout the various use of thedrawings are intended to designate similar elements or parts andwherein:

FIG. 1 is a somewhat diagrammatic perspective view of a flow box havinga portion cut away to clearly illustrate the flow element therein;

FIG. 2 is an elevational perspective view showing one of the flowpassages of the flow element in conjunction with a correspondingdiifuser nozzle;

FIG. 3 is an elevational front view of the flow element of FIG. 1showing the diffuser nozzles in alignment therewith;

FIG. 4 is an alternate embodiment with the flow element of FIG. 3; and

FIG. 5 is still another alternate embodiment of the flow element of FIG.3;

FIG. 6 is still another alternate embodiment of the flow element of FIG.3.

As seen in FIG. 1, a pre-slice chamber 10 is provided with a slice 11for delivering fibrous material in liquid suspension to a forming wire12. The forming wire 12 may be considered a continuously moving wirewhich is wrapped about a plurality of rollers, such as the roller 13.

An inlet 14 is provided for receiving stock which is to be delivered tothe slice 11. However, the stock is first delivered to a distributor 16which is in fluid communication with a plurality of diffuser nozzles 18through a corresponding number of openings or apertures 19 formed in aWall member or transverse stock flow barrier 19a. The stock is deliveredto the distributor 16 with sufi'icient pressure to cause the stock to beforced through the diffuser nozzles 18 extending downstream with agradually expanding cross-section en route to the slice 11. Thedownstream end of the diffuser nozzles 18 define a plurality of openings20 through which the stock flows at a relatively high rate. The totalcross-sectional open area of the openings 20 is substantially less thanthe total crosssectional open area of the downstream portion of the preslice chamber 10. Therefore, the stock leaving the diffuser nozzles 18will form a plurality of high velocity jet streams which slowly divergeand come together to form a substantially solid mass of stock enroute tothe slice 11. However, as the jet streams of the stock merge together,eddy currents are caused. These eddy currents are an undesirable effectin the manufacture of paper since they form clots and other deformationson the web being formed on the forming wire 12.

To eliminate such eddy currents, a flow element 21 is positioneddownstream of and in spaced relation to the diffuser element 17 and hassubstantially the same crosssectional dimension along the length thereofin the direction of the flow. The flow element 21 comprises a pluralityof flow passages 22 which are in alignment with corresponding ones ofthe diffuser nozzles 18. The crosssectional open area transverse to thestock flow of each flow passage 22 is greater than the cross-sectionalopen area of the openings 20. Therefore, the jet stream of stock willdiverge toward the side walls of the flow passages 22, therebydissipating much of the kinetic energy of the jet streams. The eddycurrents caused by the high velocity jet streams are experienced in theupstream portion of the flow passages 22, but as the stock passesthrough the flow passages, the velocity thereof is substantially reducedand the effects of eddy currents are substantially eliminated.Therefore, as the stock leaves the flow passages 22, the stock willcoalesce substantially free of eddy currents. It it is believed thatthis desirable phenomenon is accomplished by the deceleration effectwhich the flow element 21, which has a uniform cross-section along thelength thereof, offers the stock passing therethrough as well as thecross-sectional configuration of the jet stream leaving the flowelement. For example, the cross-section of the jet stream leaving thediffuser nozzles 18 is cylindrical, therefore only the tangentialperipheral portions of the jet streams initially engage one anotherthereby leaving a relatively large open area between each of the jetstreams for eddy currents to develop. On the other hand, thecross-section of the open area of the flow element 21, as seen in FIG.3, is square, thereby effectively providing a larger peripheral surfacearea between adjacent jet streams and essentially eliminating the openarea Where eddy currents might develop. Therefore, as the stock leavesthe flow element 21 it is substantially free of eddy currents and thestock will be delivered to the slice 11 in a stable manner free of clotsor other defects.

The distributor 1-6 is continuously tapered having the larger end inproximity to the inlet 14 and the smaller end in proximity to an outlet23. This feature provides a substantially uniform pressure gradientacross the apertures 19, which, in turn, cause substantially uniformflow of the stock through the diffuser nozzles 18. The outlet 23 of thedistributor 16 is connected to a secondary inlet passage 26 through aline 27. Therefore, the stock which is delivered to the distributor 16but which does not pass through the diffuser nozzle 18 is recirculatedto the sec- 4 ondary inlet 26 to combine with the stock entering theinlet 14, of the distributor 16. It will be understood that suitablepump means may be provided in the line 27 to increase the flow pressureof the stock passing therethrough.

Seen in FIG. 2 is the detail construction of one of the diffuser nozzles18 and a portion of the flow element 21 defining one of the flowpassages 22. In the illustrated embodiment of the present invention thefollowing dimensions of the diffuser nozzle 18 and the fiow passage 22have been found to give excellent results. The reduced diametercylindrical portions 30 has an axial dimension A which is equal to 4inches and an inside diameter of .8 inch. The conical portion 31 has anaxial dimension B which is equal to 10 inches. The reduced diameter endof the conical portion 31 is equal to the diameter of the cylindricalportion 30. The increased diameter portion 32 has an axial dimension Cwhich is equal to 10 inches and an inside diameter equal to 1.4 inches.It will be understood that the inside diameter of the large end of theconical portion 31 is substantially equal to the inside diameter of thecylindrical portion 32. The flow passage 22 is spaced a dimension Dwhich is three inches from the end of the diffuser nozzle 18. Theoutside dimension of the flow passage 22 is 2.75 inches square while thelength E is equal to 12v inches.

When using the specific dimensions illustrated hereinabove, the flowrates of the diffuser nozzle 18 and flow passage 22 are as follows:

At a given pressure the velocity of the stock passing through thecylindrical portion 30, is 18 feet per second. The velocity of the stockpassing through the increased diameter portion 32 of the diffuser nozzle18 is 5.88 feet per second. On the other hand, the velocity of the stockleaving the fiow passage 22 is 1.20 feet per second. Therefore, the flowpassage 22 of the flow element 21 substantially reduces the velocity ofthe stock passing through the pre-sliced chamber 10, thereby allowingthe stock to coalesce in a gentle manner and free of eddy currents. Thiseven blending of the jet streams of the stock passing through thepre-slice chamber 10 is attributed partly to the relatively large openarea at the exit of the flow element 21. By way of example, the openarea of the flow element 21 is 84% that of the cross-sectional area ofthe pre-sliced chamber downstream thereof. Comparing this to theapproximate 17% open area of the diffuser nozzles, it can be seen thatthe flow element 21 provides a substantial improvement in the manner inwhich the jet streams blend together. Also, much of the kinetic energyof the jet stream leaving the diffuser nozzle 18 is dissipated withinthe side walls of the flow passage 22 in the vicinity near the exit ofthe diffuser nozzle 18. Furthermore, the back flow in the area where thediffuser nozzles discharge into the static flow element 21 keeps theupstream edges of the compartments of the fioW element free of fiberbuildup.

Seen in FIG. 4 is an alternate embodiment of the fiow element 21. A flowpassage 22 has a rectangular crosssection. Also, the cross-section ofthe flow passages 22 may be polygonal as illustrated by the hexagonalpassages 22" shown in FIG. 5. In addition, the cross-section of the flowpassage may be round as illustrated by the passages 22 shown in FIG. 6.

Therefore, the present invention has provided a new and improved methodand apparatus for substantially eliminating eddy currents in a stockpassing through a pre-sliced chamber. Although in the illustratedembodiment of the present invention, the stationary flow element 21 isshown as being positioned downstream of the diffuser nozzle 18, it isnot to be construed in a limiting sense. Also, it will be noted that thetaper of the diffuser nozzle 18 may vary from 3 degrees to degreesincluded angle, and that other variations and modifications may beeffected without departing from the spirit and scope of the novelconcepts of this invention.

We claim as our invention:

1. A method of supplying paper stock to the travelling forming wire of apapermaking machine comprising the steps of:

establishing a flow of paper stock,

dividing the flow into a plurality of parallel diverging diffusernozzles for reducing the velocity of the streams therethrough,

discharging said streams from cylindrically-shaped outlets of saiddiffuser nozzles to a corresponding plurality of parallel flow passagesaligned with said difi'user nozzles and having larger cross-sectionalareas than the outlets of said diffuser nozzles and spaced therefrom toenable said streams to diverge therebetween to create turbulence and toconvert kinetic energy to pressure and to reduce the velocity of thestreams as they move through the flow passages,

discharging the streams from the flow passages and merging them into asingle stream, and

directing the single stream to the travelling wire of a papermakingmachine.

2. Apparatus for supplying paper stock to a papermaking machinecomprising:

means forming a slice and a pre-slice flow chamber connected to saidslice for directing a flow of paper stock to said slice,

said slice being downstream of said chamber,

a portion of said chamber forming means defining a transverse stock flowbarrier having a plurality of circular apertures formed therein ingenerally parallel spaced relation,

a plurality of spaced generally parallel stock diffuser nozzlesconnected to said barrier each in alignment with a corresponding one ofsaid apertures and in each case having an upstream cross-sectional areathat is the same as the aperture cross-sectional area and extendingdownstream with a gradually expanding cross-section to define a circulardischarge opening greater than the aforesaid cross-sectional area,

a flow element positioned in spaced relation to and downstream of saiddifiuser nozzles having substantially the same cross-sectional dimensionalong the length thereof in the direction of said flow for reducing theeffects of eddy currents of the paper stock passing through the flowchamber,

said flow element comprising means forming a plurality of flow passagesof uniform cross-section along the length thereof aligned respectivelywith said difiuser nozzles,

the cross-section of each said flow passages transverse to the flowbeing greater than the cross-section of the discharge opening of itscorresponding immediately upstream diffuser nozzle, and distributormeans upstream of said chamber for delivering paper stock to thediffuser nozzles at a substantially uniform pressure.

3. The apparatus of claim 2 wherein said distributor means comprisesmeans forming a stock inlet and a stock outlet and including circulatingmeans connected to said stock outlet for receiving surplus stocktherefrom which does not pass through said diffuser nozzles anddelivering such surplus stock back to said stock inlet.

4. The apparatus of claim 2 wherein each of said flow passages has arectangular cross-sectional configuration transverse to the stock flow.

5. The apparatus of claim 2 wherein each of said flow passages has asquare cross-sectional configuration transverse to the stock flow.

6. The apparatus of claim 2 wherein each of said flow passages has apolygonal cross-sectional configuration transverse to the stock flow.

7. The apparatus of claim 2 wherein each of said flow passages has ahexagonal cross-sectional configuration transverse to the stock flow.

8. The apparatus of claim 2 wherein the total crosssectional area ofsaid flow passages is greater than the total area of the dischargeopening of said difiuser nozzles.

References Cited UNITED STATES PATENTS 3,400,044- 9/1968 Justus 162343S. LEON BASHORE, Primary Examiner R. H. TUSHIN, Assistant Examiner US.Cl. X.R. 162-343

